1) How long's a piece of string? You can veg 10 seeds and all 10 turn out male, or all 10 female of 5 male and 5 female - it's the luck of the draw. Grown out in optimum conditions you should get 50% female/male. In my last grow I grew out 3 seeds - two turned out male with 1 female.

2) It's not wise to veg plants, flower them to determine sex and then re-veg them again it confuses and stresses the plants and dimishes their genetic integrity. Better to take clones from your vegging plants and root them under 12/12 and within 10-14 days you should know the sex of each plant.

3) See above.

1) Hermies are considered 'undesirable' simply because they can pollinate your other females once the pollen sacks open and because male parts on a hermie plant often aren't that easy to spot - you can miss them quite easily.

2) Male flowers appear on a predominantly female plant.

3) You shouldn't worry about your plants turning hermie at all. If you grow them properly, keep your lighting schedules consistent, don't over-fertilise or under fertilise and water correctly there should be no reason for them to turn hermie. Some do so genetically, some do so via environmental stress - but it's not something to worry about - if you spot male flowers on a female plant either nip them off or destroy it.

Good luck with your endeavours.